As a conveyor device for transporting articles, a device of the type (so-called belt conveyor) is available that transports articles on a belt revolving between a plurality of pulleys, the belt being wrapped around the pulleys.
Such a conveyor device may vary the accuracy of a positional relationship between the pulleys (e.g., parallelism accuracy) or the accuracy of form between the own pulleys (e.g., diameter accuracy) or cause an external force to an article to be conveyed on the belt. In this case, the position of the belt on the outer surface of the pulley may laterally deviate from the center of the outer surface (cylinder side) of the pulley with respect to the transporting direction, that is, mistracking may occur.
In an ordinary belt conveyor, the surface of a pulley is worked (crowned) so as to protrude the central part of the outer surface of the pulley. The belt revolving between pulleys comes close to the protrusion (crown effect), so that mistracking is unlikely to occur. Moreover, the accuracy of the positional relationship and the accuracy of form has been increased to prevent mistracking as much as possible.
However, it is difficult to form/place various components with completely ideal accuracy. Even if high accuracy is obtained, the used pulleys and belt may be slightly deformed by friction or a temperature change, leading to difficulty in completely preventing mistracking for an extended period.
Thus, a conveyor device may have a mistracking regulating function that corrects a belt position in the event of mistracking so as to eliminate the mistracking.
For example, FIG. 7 shows a conveyor device 90 that is a double conveyor provided with two right and left belts 92 for transporting an article 93. The belts 92 travel in a transporting direction with the article 93 hung between the right and left belts 92, thereby transporting the article 93 in the transporting direction. In the conveyor device 90, a frame 91 supports both ends of a shaft 96 that pivotally supports a pulley 94 having the wrapped belt 92. Both ends of the shaft 96 can be longitudinally moved along the transporting direction of the article 93 by the rotation of a handle 98.
Moving both ends of the shaft 96 by the same amount changes a distance between the illustrated pulley 94 and a pulley (not shown) opposite to the pulley 94 in the transporting direction, regulating the tension of the belt 92 looped between the pulleys. Moving only one end of the shaft 96 inclines the orientation of the pulley 94. This changes the position of the traveling belt 92 on the pulley 94 so as to regulate mistracking.
Japanese Patent Laid-Open No. 2004-210447 describes a method in which a tension pulley with a weight is disposed under a conveyor device and a belt is wrapped around the tension pulley. In this method, a tension is applied to the belt by the load of the weight and the load is evenly distributed to both sides of the tension pulley. This suppresses unevenness in the vertical movement of the tension pulley, thereby preventing mistracking of the belt.
In the conventional method of FIG. 7, however, even if an operator moves only one end of the shaft 96 to regulate mistracking, the position of the pulley 94 slightly changes in the transporting direction and thus the tension of the belt 92 also changes. In the regulation of tension, the operator moves both ends of the shaft 96 by completely the same amount, thereby changing only the tension without changing the orientation of the pulley 94. However, even a small difference in the amount of movement between one end and the other end may change the orientation of the pulley 94, causing mistracking. Since it is difficult to move both ends of the shaft 96 by completely the same amount, mistracking regulation is always necessary after the tension regulation. In this way, the mistracking regulation and the tension regulation affect each other. It is difficult for the operator to separately regulate only one of mistracking and tension. Thus, the operator needs to carefully move both ends of the shaft 96 in consideration of a mistracking state and a tension state. This causes the operator difficulty in regulating mistracking and tension with an extended period.
Since the frame 91 is disposed on the right and left sides of the pulley 94 having the wrapped belt 92, the frame 91 outside the belt 92 needs to be disassembled to remove the belt 92 from the pulley 94 during replacement of the belt 92. After the replacement of the belt 92, the disassembled frame 91 needs to be reassembled. Since the shaft 96 is removed from the frame 91 at the time of disassembling of the frame 91, the positional relationship between the reassembled frame 91 and the shaft 96 is reset to the initial assembling state of the frame 91. Thus, even if a mistracking state and a tension state are properly set before disassembling, it is necessary to regulate mistracking and tension again through the difficult and time-consuming operation after reassembling. Therefore, in the conventional method of FIG. 7, the replacement of the belt 91 requires disassembling and reassembling of the frame 91 and regulation of mistracking and tension from the initial assembling state of the frame 91. For this reason, the conventional method considerably consumes much time and effort of an operator.
Moreover, the method using the weight requires a space for installing the weight under the conveyor device and thus is not applicable to a conveyor device that transports an article on a transporting surface located near the floor surface of equipment, that is, a so-called low profile conveyor.
An object of the present invention is to provide a conveyor device that reduces time and effort for regulating mistracking and replacing belts and eliminates the need for a large space for a mistracking regulating mechanism.